Dr Katy Sinka, head of sexually transmitted infections at UKHSA, said genomic testing had allowed it to be detected.
“It’s normal for viruses to evolve, and further analysis will help us understand more about how mpox is changing.
“Getting vaccinated is a proven effective way to protect yourself against severe disease, so please make sure to get the jab if you are eligible,” she said.
Prof Trudie Lang, director of the Global Health Network at the University of Oxford, said there were “excellent systems” to identify cases and control onward infection in the UK, but in other parts of the world, in more vulnerable populations, “this is harder to achieve”, where access to vaccines is not as reliable.
Prof Lang said if further cases of this strain appeared in the UK and elsewhere, it would be important to understand how it’s being spread and how ill it makes people, in order to assess whether it’s more or less dangerous than previous strains.
There have been nearly 48,000 confirmed cases of mpox globally in 2025, and 2,500 in the past month, with most occurring in central Africa.
Dr Boghuma Titanji, assistant professor of medicine at Emory University, said the new strain is what experts feared would happen if mpox continued to spread worldwide.
“The more mpox circulation we permit, the more opportunities the virus has to recombine and adapt, further entrenching mpox virus as a human pathogen that is not going away,” she said.
